Improved performance for .NET 9.0+ using the new System.Threading.Lock.

src/Directory.Build.props

@@ -19,6 +19,10 @@
   <PropertyGroup Condition=" '$(TargetFramework)' == 'net8.0'">
     <DefineConstants>Core;NET80</DefineConstants>
   </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'net9.0'">
+    <DefineConstants>Core;NET90</DefineConstants>
+  </PropertyGroup>	
 
   <PropertyGroup Condition=" '$(TargetFramework)' == 'net481'">
     <DefineConstants>NET481;NETFULL</DefineConstants>

src/Directory.Packages.props

@@ -13,6 +13,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageVersion Include="Backport.System.Threading.Lock" Version="1.1.1" />
     <PackageVersion Include="FakeItEasy" Version="8.0.0" />
     <PackageVersion Include="Microsoft.CSharp" Version="4.7.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />

src/EPPlus.Interfaces/EPPlus.Interfaces.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
-		<TargetFrameworks>net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0;net462;net35</TargetFrameworks>
+		<TargetFrameworks>net9.0;net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0;net462;net35</TargetFrameworks>
 		<AssemblyVersion>6.1.1.0</AssemblyVersion>
 		<FileVersion>6.1.1.0</FileVersion>
 		<Version>6.1.1</Version>

src/EPPlus.System.Drawing/EPPlus.System.Drawing.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0;net462;net35</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0;net462;net35</TargetFrameworks>
     <AssemblyVersion>6.1.1.0</AssemblyVersion>
     <FileVersion>6.1.1.0</FileVersion>
     <Version>6.1.1</Version>

src/EPPlus/Core/CellStore/CellStore.cs

@@ -49,7 +49,7 @@ internal static class CellStoreSettings
     /// </summary>
     internal class CellStore<T> : IDisposable
     {
-        private readonly static object _syncRoot = new object();
+        private readonly static Lock _syncRoot = new Lock();
         internal ColumnIndex<T>[] _columnIndex;
         internal int ColumnCount;
         public bool IsReadonly { get; set; }

src/EPPlus/Core/CellStore/ColumnIndex.cs

@@ -12,12 +12,13 @@ Date               Author                       Change
  *************************************************************************************************/
 using System;
 using System.Collections.Generic;
+using System.Threading;
 
 namespace OfficeOpenXml.Core.CellStore
 {
     internal class ColumnIndex<T> : IndexBase, IDisposable
     {
-        private readonly static object _syncRoot = new object();
+        private readonly static Lock _syncRoot = new Lock();
         internal List<T> _values = new List<T>();
         internal PageIndex[] _pages;
         internal int PageCount;

src/EPPlus/Core/Worksheet/Fonts/GenericFontMetrics/GenericFontMetricsTextMeasurerBase.cs

@@ -17,14 +17,15 @@ Date               Author                       Change
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using System.Threading;
 
 namespace OfficeOpenXml.Core.Worksheet.Fonts.GenericFontMetrics
 {
     internal abstract class GenericFontMetricsTextMeasurerBase
     {
         private FontScaleFactors _fontScaleFactors = new FontScaleFactors();
         private static Dictionary<uint, SerializedFontMetrics> _fonts;
-        private static object _syncRoot = new object();
+        private static Lock _syncRoot = new Lock();
 
         public GenericFontMetricsTextMeasurerBase()
         {

src/EPPlus/EPPlus.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
-		<TargetFrameworks>net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0;net462;net35</TargetFrameworks>
+		<TargetFrameworks>net9.0;net8.0;net7.0;net6.0;netstandard2.1;netstandard2.0;net462;net35</TargetFrameworks>
 		<AssemblyVersion>7.2.2.0</AssemblyVersion>
 		<FileVersion>7.2.2.0</FileVersion>
 		<Version>7.2.2</Version>
@@ -505,7 +505,7 @@
 		<SignAssembly>true</SignAssembly>
 		<AssemblyOriginatorKeyFile>OpenOfficeXml.snk</AssemblyOriginatorKeyFile>
 		<NeutralLanguage />
-		<LangVersion>latest</LangVersion>
+		<LangVersion>preview</LangVersion>
 		<PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
 		<RepositoryType>git</RepositoryType>
 		<PackageIcon>EPPlusLogo.png</PackageIcon>
@@ -565,6 +565,10 @@
 		<PackageReference Include="System.Text.Encoding.CodePages" />
 	</ItemGroup>
 
+	<ItemGroup Condition="'$(TargetFramework)' == 'net35' or '$(TargetFramework)' == 'net462' or '$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'netstandard2.1' or '$(TargetFramework)' == 'net6.0' or '$(TargetFramework)' == 'net7.0' or '$(TargetFramework)' == 'net8.0'">
+		<PackageReference Include="Backport.System.Threading.Lock" />
+	</ItemGroup>
+
 	<ItemGroup>
 		<Compile Remove="LoadFunctions\HeaderReader.cs" />
 	</ItemGroup>

src/EPPlus/FontSize.cs

@@ -17,6 +17,7 @@ Date               Author                       Change
 using System.IO;
 using System.Text;
 using OfficeOpenXml.Utils;
+using System.Threading;
 
 namespace OfficeOpenXml
 {
@@ -35,7 +36,7 @@ public class FontSize
         /// </summary>
         public const string NonExistingFont = "Arial";
         internal static bool _isLoaded = false;
-        internal static object _lockObj=new object();
+        internal static Lock _lockObj = new Lock();
         internal static MemoryStream _fontStream=null;
         /// <summary>
         /// Dictionary containing Font Width in pixels.

src/EPPlus/FormulaParsing/Excel/Functions/ArgumentParsers.cs

@@ -11,6 +11,7 @@ Date               Author                       Change
   01/27/2020         EPPlus Software AB       Initial release EPPlus 5
  *************************************************************************************************/
 using System.Collections.Generic;
+using System.Threading;
 using OfficeOpenXml.FormulaParsing.FormulaExpressions;
 using OfficeOpenXml.FormulaParsing.Utilities;
 
@@ -21,7 +22,7 @@ namespace OfficeOpenXml.FormulaParsing.Excel.Functions
     /// </summary>
     internal class ArgumentParsers
     {
-        private static object _syncRoot = new object();
+        private static Lock _syncRoot = new Lock();
         private readonly Dictionary<DataType, ArgumentParser> _parsers = new Dictionary<DataType, ArgumentParser>();
         private readonly ArgumentParserFactory _parserFactory;
 

src/EPPlus/FormulaParsing/Excel/Functions/Engineering/Conversions.cs

@@ -13,6 +13,7 @@ Date               Author                       Change
 using System;
 using System.Collections.Generic;
 using System.Text;
+using System.Threading;
 using MathObj = System.Math;
 
 namespace OfficeOpenXml.FormulaParsing.Excel.Functions.Engineering
@@ -80,7 +81,7 @@ public Prefix(string abbrevation, double value)
         private static List<Prefix> _metricPrefixes = null;
         private static List<Prefix> _binaryPrefixes = null;
         private static bool _initialized = false;
-        private static object _syncRoot = new object();
+        private static Lock _syncRoot = new Lock();
 
         #region Initialization methods
 

src/EPPlus/FormulaParsing/ExcelAddressCache.cs

@@ -13,6 +13,7 @@ Date               Author                       Change
 using System;
 using System.Collections.Generic;
 using System.Text;
+using System.Threading;
 
 namespace OfficeOpenXml.FormulaParsing
 {
@@ -21,7 +22,7 @@ namespace OfficeOpenXml.FormulaParsing
     /// </summary>
     public class ExcelAddressCache
     {
-        private readonly object _myLock = new object();
+        private readonly Lock _myLock = new Lock();
         private readonly Dictionary<int, string> _addressCache = new Dictionary<int, string>();
         private readonly Dictionary<string, int> _lookupCache = new Dictionary<string, int>();
         private int _nextId = 1;

src/EPPlus/Packaging/DotNetZip/WinZipAes.cs

@@ -32,6 +32,7 @@
 using System.IO;
 using System.Collections.Generic;
 using System.Security.Cryptography;
+using System.Threading;
 
 #if AESCRYPTO
 namespace OfficeOpenXml.Packaging.Ionic.Zip
@@ -310,7 +311,7 @@ internal static string FormatByteArray(byte[] b)
     }
 
 #endif
-    #endregion
+#endregion
 
 
 
@@ -935,7 +936,7 @@ private void TraceOutput(string format, params object[] varParams)
             }
         }
 
-        private object _outputLock = new Object();
+        private Lock _outputLock = new Lock();
     }
 }
 #endif

src/EPPlus/Packaging/DotNetZip/ZipEntry.Write.cs

@@ -29,6 +29,7 @@
 using OfficeOpenXml.Packaging.Ionic.Zlib;
 using System;
 using System.IO;
+using System.Threading;
 using RE = System.Text.RegularExpressions;
 
 namespace OfficeOpenXml.Packaging.Ionic.Zip
@@ -2559,6 +2560,6 @@ private void TraceWriteLine(string format, params object[] varParams)
             }
         }
 
-        private object _outputLock = new Object();
+        private Lock _outputLock = new Lock();
     }
 }

src/EPPlus/Packaging/DotNetZip/ZipFile.cs

@@ -44,6 +44,7 @@
 using System.Reflection;
 using Interop = System.Runtime.InteropServices;
 using OfficeOpenXml.Packaging.Ionic.Zlib;
+using System.Threading;
 namespace OfficeOpenXml.Packaging.Ionic.Zip
 {
     /// <summary>
@@ -3622,7 +3623,7 @@ private Stream WriteStream
         private bool _hasBeenSaved;
         private String _TempFileFolder;
         private bool _ReadStreamIsOurs = true;
-        private object LOCK = new object();
+        private Lock LOCK = new Lock();
         private bool _saveOperationCanceled;
         private bool _extractOperationCanceled;
         private bool _addOperationCanceled;

src/EPPlus/Packaging/DotNetZip/Zlib/ParallelDeflateOutputStream.cs

@@ -112,7 +112,7 @@ public class ParallelDeflateOutputStream : System.IO.Stream
         private AutoResetEvent              _newlyCompressedBlob;
         //private ManualResetEvent            _writingDone;
         //private ManualResetEvent            _sessionReset;
-        private object                      _outputLock = new object();
+        private Lock                        _outputLock = new Lock();
         private bool                        _isClosed;
         private bool                        _firstWriteDone;
         private int                         _currentlyFilling;
@@ -121,14 +121,14 @@ public class ParallelDeflateOutputStream : System.IO.Stream
         private int                         _latestCompressed;
         private int                         _Crc32;
         private Ionic.Crc.CRC32             _runningCrc;
-        private object                      _latestLock = new object();
+        private Lock                        _latestLock = new Lock();
         private System.Collections.Generic.Queue<int>     _toWrite;
         private System.Collections.Generic.Queue<int>     _toFill;
         private Int64                       _totalBytesProcessed;
         private Ionic.Zlib.CompressionLevel _compressLevel;
         private volatile Exception          _pendingException;
         private bool                        _handlingException;
-        private object                      _eLock = new Object();  // protects _pendingException
+        private Lock                        _eLock = new Lock();  // protects _pendingException
 
         // This bitfield is used only when Trace is defined.
         //private TraceBits _DesiredTrace = TraceBits.Write | TraceBits.WriteBegin |

src/EPPlus/Utils/RecyclableMemory.cs

@@ -62,7 +62,7 @@ internal class RecyclableMemory
 	{
 #if !NET35
 		private static RecyclableMemoryStreamManager _memoryManager;
-		private static object _dataLock = new object();
+		private static Lock _dataLock = new Lock();
 
 		public static bool UseRecyclableMemory { get; set; } = true;
 		internal static bool HasMemoryManager

src/EPPlus/Utils/StreamUtil.cs

@@ -20,7 +20,7 @@ namespace OfficeOpenXml.Utils
 {
     internal class StreamUtil
     {
-        static object _lock = new object();
+        static Lock _lock = new Lock();
         /// <summary>
         /// Copies the input stream to the output stream.
         /// </summary>